Yes on a true indication

Yes on a test light confirming power of the voltage

If there is a constriction / bad splice the voltage will be traded for current and vice versa , a meter is not drawing much current to read

Pin 18

pin 18 closes the ECU Controlled relay that when closed brings power back into the ECU from a fuse X , power sitting on the injectors ( this time and only ) and 1 / 2 of your engine sensors

If your pin is broken you can jumper the relay between socket 3 and 5 with a medium gauge jumper wire < blade type jumper wire ends

 

You can make a test lamp from a spare 12 volt bulb

if you use too small a watt bulb the test would be inconclusive , too large like a headlight might blow a fuse

 

My new ECU turned up in the post. A 1994 4.0 ECU, but it worked in my car. It now runs on all 6 cylinders! Wahey!

I’m trying to find the leak as we have a lot of rain coming the next few days. Currently hitting the windscreen with a hose to try and find any water ingress. Where are the drains around the screen I should be looking for? The two large ones that say LEFT and RIGHT on them under windscreen wiper surround?

The rubber flap I adjusted on the wiper plenum has now fallen off somewhere, I adjusted it badly obviously. What happens if I drive without this flap in the rain? Will water leak into the ECU area? Also, where can I buy one of these flaps?

I’ve sprayed loads of water around the windscreen, none appearing at the ECU. Hopefully the blocked plenum was the cause of the leak. For now, I’ve made a makeshift plenum valve out of heavy duty tape, with enough of a gap at the side to let water out. We’ll see how she holds up after a week of British winter rain.

 

If you extend a large tube to the bottom of the car , this would prevent the positive air pressure in the engine compartment from backing up the tube's flow

If you remove the large black rectangle from the rear engine fire wall the sliding clips around the perimeter can fail to slide to disconnect

A hooked coat hanger used in a manner of a sling hammer can slid them over after some clips soaking with some heavy grease

This is usually the bottom 2 clips

Pay attention to your new idle speed as it settles down with your replaced ECU

 

Hello all, I just wanted to confirm that’s it’s been some time now, through lots of heavy rain, and the problem has not reoccurred. My ECU plugs are dry, startup has been easy (besides a short grinding noise on startup which I think is unrelated, probably oil drain), and the Jag has been running smooth since the new ECU. Even the idle has decreased a bit to an acceptable level.

Thank you to all who contributed to getting this old Sovereign back on the road, especially Parker, all the diagnostic tips and advice were very helpful. For now, I’ll consider this case closed.

 

There are some oil viscosity recommendations, and this uprated valve chain tensioner

The tensioner has to pump up and expand on startup , but there should be some trapped piston extending oil from last engine run

A oil treatment to un gummy the expanding piston ?

The uprated tensioner will have the big arrow cast on the tensioner

If swapping out ( sourced from a salvage yard ) the uprated version takes longer mount bolts so be sure to get those from the donor car

03-1-09 Rattle After Start.pdf (jagrepair.com)